Scientists in Denmark say they’re close to a “promising” breakthrough to cure human immunodeficiency virus, HIV.

Researchers at the Aarhus University Hospital are conducting clinical trials on humans using a “novel strategy” proven effective in laboratory tests. The news came just days after the U.S. government announced failure in a large study to develop a possible HIV vaccine.

The Danish study uses a therapy that flushes the virus from so-called reservoirs it forms within DNA cells, whereupon the body’s immune system — with a little help from a vaccine — can hunt and destroy. Though the therapy appeared effective when using human skin cells in the lab, efficacy in the human body remains unproven, according to Dr. Ole Sogaard, a senior researcher in the department of infectious disease.

“The challenge will be getting the patients’ immune system to recognize the virus and destroy it. This depends on the strength and sensitivity of individual immune systems,” Dr. Sogaard told the media.